Method for optimizing off-line facial feature tracking

ABSTRACT

The present invention relates to a technique for optimizing off-line facial feature tracking. Facial features in a sequence of image frames are automatically tracked while a visual indication is presented of the plurality of tracking node locations on the respective image frames. The sequence of image frames may be manually paused at a particular image frame in the sequence of image frames if the visual indication of the tracking node locations indicates that at least one location of a tracking node for a respective facial feature is not adequately tracking the respective facial feature. The location of the tracking node may be reinitialized by manually placing the tracking node location at a position on the particular image frame in the monitor window that corresponds to the respective facial feature. Automatic tracking of the facial feature may be continued based on the reinitialized tracking node location.

BACKGROUND OF THE INVENTION

The present invention relates to avatar animation, and more particularly, to facial feature tracking.

Animation of photo-realistic avatars or of digital characters in movie or game production generally requires tracking of an actor's movements, particularly for tracking facial features. Accordingly, there exists a significant need for improved facial feature tracking. The present invention satisfies this need.

SUMMARY OF THE INVENTION

The present invention is embodied in a method, and related apparatus, for optimizing off-line facial feature tracking. In the method a monitor window is provided that has a visual indication of a plurality of tracking node locations with respect to facial features in a sequence of image frames. The monitor window has a control for pausing at an image frame in the sequence of image frames. The facial features in the sequence of image frames are automatically tracked while the visual indication is presented of the plurality of tracking node locations on the respective image frames. The sequence of image frames may be manually paused at a particular image frame in the sequence of image frames if the visual indication of the tracking node locations indicates that at least one location of a tracking node for a respective facial feature is not adequately tracking the respective facial feature. The location of the tracking node may be reinitialized by manually placing the tracking node location at a position on the particular image frame in the monitor window that corresponds to the respective facial feature. Automatic tracking of the facial feature may be continued based on the reinitialized tracking node location.

In other more detailed features of the invention, the tracking of facial features in the sequence of facial image frames of the speaking actor may performed using bunch graph matching, or using transformed facial image frames generated based on wavelet transformations, such as Gabor wavelet transformations.

Other features and advantages of the present invention should be apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram for illustrating a method for optimizing off-line facial feature tracking using manual reinitialization of track node location, according to the present invention.

FIG. 2 is a schematic diagram of a monitor window for providing a visual indication of a plurality of tracking node locations with respect to facial features in a sequence of image frames for use in the method for off-line facial feature tracking of FIG. 1.

FIG. 3 is a schematic diagram of a monitor window for providing a visual indication of a plurality of tracking node locations with respect to facial features in a sequence of image frames for use in the method for optimizing off-line facial feature tracking of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a technique for optimizing facial feature tracking for extraction of animation values or parameters. Automatic extraction generally increases the speed and reduces the tedium associated with the extraction task. Manual intervention permits correction of tracking inaccuracies or imperfections that may reduce the desirability of automatic extraction.

With reference to FIG. 1, the invention may be embodied in a method, and related apparatus, for optimizing off-line facial feature tracking. In the method, a monitor window 22 is provided that has a visual indication of a plurality of tracking node locations 24 with respect to facial features in a sequence of image frames 26 (step 12). The monitor window has a control 28 for pausing at an image frame in the sequence of image frames. The facial features in the sequence of image frames are automatically tracked while the visual indication is presented of the plurality of tracking node locations on the respective image frames (step 14). The sequence of image frames may be manually paused at a particular image frame in the sequence of image frames if the visual indication of the tracking node locations indicates that at least one location 24-1 of a tracking node for a respective facial feature is not adequately tracking the respective facial feature (step 16). The location of the tracking node may be reinitialized by manually placing the tracking node location at a position 24-1′ on the particular image frame in the monitor window that corresponds to the respective facial feature (step 18). Automatic tracking of the facial feature may be continued based on the reinitialized tracking node location (step 20).

The tracking of facial features in the sequence of facial image frames of the speaking actor may performed using bunch graph matching, or using transformed facial image frames generated based on wavelet transformations, such as Gabor wavelet transformations. Wavelet-based tracking techniques are described in U.S. Pat. No. 6,272,231. The entire disclosure of U.S. Pat. No. 6,272,231 is hereby incorporated herein by reference. The techniques of the invention may be accomplished using generally available image processing systems.

The manual intervention allows scalability of the animation tracking. For high quality animation, frequent manual interaction may be employed to insure accurate tracking. For lower quality animation, manual interaction may be employed less frequently for correcting only significant inconsistencies.

Although the foregoing discloses the preferred embodiments of the present invention, it is understood that those skilled in the art may make various changes to the preferred embodiments without departing from the scope of the invention. The invention is defined only by the following claims. 

We claim:
 1. Method for optimizing off-line facial feature tracking, comprising the steps for: providing a monitor window that has a visual indication of a plurality of tracking node locations with respect to facial features in a sequence of image frames, the monitor window having a control for pausing at an image frame in the sequence of image frames; automatically tracking the facial features in the sequence of image frames while presenting the visual indication of the plurality of tracking node locations on the respective image frames; manually pausing the sequence of image frames at a particular image frame in the sequence of image frames if the visual indication of the tracking node locations indicates that at least one location of a tracking node for a respective facial feature is not adequately tracking the respective facial feature; reinitializing the at least one location of the tracking node by manually placing the tracking node location at a position on the particular image frame in the monitor window that corresponds to the respective facial feature; and continuing automatic tracking of the facial feature based on the reinitialized at least one tracking node location.
 2. Method for optimizing off-line facial feature tracking as defined in claim 1, wherein the tracking of facial features in the sequence of facial image frames of the speaking actor is performed using bunch graph matching.
 3. Method for optimizing off-line facial feature tracking as defined in claim 1, wherein the tracking of facial features in the sequence of facial image frames of the speaking actor is performed using transformed facial image frames generated based on wavelet transformations.
 4. Method for optimizing off-line facial feature tracking as defined in claim 1, wherein the tracking of facial features in the sequence of facial image frames of the speaking actor is performed using transformed facial image frames generated based on Gabor wavelet transformations.
 5. Apparatus for optimizing off-line facial feature tracking, comprising: a monitor window means for providing a visual indication of a plurality of tracking node locations with respect to facial features in a sequence of image frames, the monitor window having a control for pausing at an image frame in the sequence of image frames; means for automatic tracking of the facial features in the sequence of image frames while presenting the visual indication of the plurality of tracking node locations on the respective image frames; means for manually pausing the sequence of image frames at a particular image frame in the sequence of image frames if the visual indication of the tracking node locations indicates that at least one location of a tracking node for a respective facial feature is not adequately tracking the respective facial feature; means for reinitializing the at least one location of the tracking node by manually placing the tracking node location at a position on the particular image frame in the monitor window that corresponds to the respective facial feature; and means for continuing automatic tracking of the facial feature based on the reinitialized at least one tracking node location. 